Suction muffler for airplanes, automobiles, and the like



March 7, 1944. Q FlSHER 2,343,371

SUCTION MUFFLER FOR AIRPLANES, AUTOMOBILES, AND THE LIKE Filed Sept. 9,1941 IN ENTOR W yaw l I ORNEY Patented Mar. 7, 1944 SUCTION MUFFLER FORAIBPLANES, AUTOMOBILES, AND THE LIKE John A. Fisher, Steinhatchee, Fla.Application September 9, 1941, Serial No. 410,138

Claims.

My invention comprises certain new and useful improvements in mufllersfor internal combustion engines, especially those of airplanes andautomobiles, and its principal purpose is the elimination or minimizingof all detrimental back pressure in-the exhaust gases and the reductionof the sounds of the motor explosions to an unobiectionable minimumbefore and during the discharge or evacuation of the exhaust gases fromthe motor.

In the internal combustion engine art it has long been recognized thatin the case of the types of muiilers now in use a great power loss iscaused by the back pressure of the exhaust gases, including atmosphericand other restrictive presures, and also that means are desirable toreiuce the sound of the motor explosions.

These considerations are of very great importance in the case ofairplanes as the reduction of atmospheric back pressure against theexhaust gases of the motor results in an increase of the available powerand consequently in the speed of travel, and the reduction in the soundrenders it more diflicult to detect at a distance the approach of anairplane in times of war or to determine by the sound of its motor thenationality of the-approaching plane.

At present it is the accepted practice in the case of airplanes todischarge the exhaust gases along with the explosive sounds directlyinto the compact air of the slip stream, where such noises blend andpartially synchronize with the slashing or ping-like noises of thewhirling propeller, which latter noises, without this blending andsynchronization, would not be audible beyond a relatively shortdistance; and thus the approach of an airplane is audibly heralded longbefore the approaching airplane becomes visible to observers.

With these advantageous ends in view I have invented a new and improvedmuilier structure which provides an induced suction efiect whereby theexhaust gases emerge into a belt or zone of rarifled air, thuseliminating back pressure, and also subduing the noises of explosioninasmuch as noises cannot be produced or transmitted in a vacuum, and ina highly rarifled atmosphere or partial vacuum they are effectuallydampened and their transmittal reduced to a minimum.

Again, due to the internal structure and contour of my improved muiiler,the noises are so baiiled and absorbed as to be materially reduced evenat low speeds of travel of the airplane.

However, the greater the speed of travel of the airplane, theatmospheric air at the tall or discharge end of the muilier is rarifledand its pressure reduced to a greater degree, and thus the efliciency ofmy improved muiller both in reducing back pressures of any kindwhatsoever and noise increases in a commensurate degree with the speedof travel.

In the accompanying drawing, wherein I have illustrated a practicalembodiment of the principles of my invention,

a Fig. 1 is a top plan view of the suction muf- Fig. 2 is a sideelevation of the same, partially in section;

' Fig. 3 is an end view lokoing from the right in Figs. 1 and 2;

Fig. 4' is a side view, partially in section, showing an application ofthe principles of my inven tion to the nacelle or cover of the motormounted on the wing of an airplane;

Fig. 5 is a side elevation illustrating the principles of my inventionapplied to an airplane, the motor of which is mounted on the fuselage;

Fig. 6 is a broken front elevation of the strumture illustrated in Fig.5;

Fig. 7 is a broken side elevation showing theprinciples of my inventionapplied to an automobile;

Fig. 8 is a view similar to Fig. 3 but illustrating a modification.

Referring first to Figs. 1 to 4, inclusive, l0 indicates the body of themuiiier which is of flattened form, having a materially greater internalwidth than vertical height. II indicates the mouth of the body III whichis centrally located in the front wall of the body and is of annularform and of proper dimensions to be attachable directly tothe exhaustmanifold. or the pipe leading from the latter. The contour of the frontwall of the body is curvilinear to produce a neck and provide ahorizontally expanding path of travel for the exhaust gases. The mouth II may be provided with a perimetral flange Ila, as shown in the drawingfor the ready attachment of the muiiier to the exhaust exit of themotor. The body may, for the sake of convenience and economy ofconstruction be formed of two sections, upper and lower, which arejoined along the lines indicated at IS in Fig. 1, in any convenient andwell known manner.

The chamber formed interiorly of the body i0 is of such shape orrelative dimensions as to direct the exhaust gases in the form of a widebut relatively shallow stream as they flow toward and into beige tailbox I4 hereinafter more tully descri To facilitate such direction andformation of the stream of exhaust gases I provide in the top wall ofthe body It] a dent or depression located somewhat to the'rear butadjacent to the mouth of the body and of rearwardly diverging side wallswhich may advantageously more or less parallel the diverging innersurfaces of the front wall of the body. This provision materially aidsin laterally spreading and widening the stream of gases entering throughthis mouth II.

The top and bottom walls of the body gradually converge, as shown inFig. '2, to further shallow the stream of gases.

It will be seen that the structure of the body as illustrated in Figs. 1and 2 is such that it has no interior angles or surfaces which mightreflect the sound waves directly toward the rear of the body. The sidewalls of the body are preferably parallel or may even converge slightlytoward the rear end of the body.

An important concept of my invention is that the chamber provided by thebody be such so that the gases introduced thereinto by the succession ofexplosion puffs or blasts, incident to the operation of the motor, havesuflicient volumetric space to spread and expand laterally and toobviate choking or back pressure. The gradual con vergence of the topand bottom walls of the flat body ll! serves to deflect, confine andabsorb most of the firing noises and produce a thin or shallow butwidely spread stream of gases which thus formed can carry but littlesound.

The vertical bend or curve aids in the convenient positioning of thetail end of the mufller and also aids in the spreading of the exhauststream as it travels rearwardly, thus restricting sound.

I The outlet of the body In is thus a widely extended but verticallyrestricted slotted opening.

The tail box I is of the full width of the body but interiorly ofmaterially greater vertical height to augment suction effect. In itsfront wall it is provided with a horizontal slotted opening l6 extendedfor the width of the tail box and of equal horizontal length with theexit opening of the body which it matches. For convenience ofattachment, the edges of the opening l6 may be provided with anoutwardly extending spaced flange 16a which may fit over the end of thebody It and be secured thereto as by welding or bolts.

The top, bottom and sides of the tail box I are closed, but the rear endof the tail box is open, except as hereinafter explained.

l1 represents a baflle which is mounted horizontally in the tail box l4and held in place as by the end flanges l8 which fit against theinterior surfaces of the tail box and are welded or otherwise securedthereto. The baflle I1 is provided with an arcuate surface facing thedirection from which the stream of gases flows, and said baflle ispreferably of cylindrical cross sectional shape.

The bafile I1 is placed adJacent but to the rear of the entrance openingl6 of the tail box and the baffle is of such diameter as to providepassages l9 above and below the baffle extending to the full width ofthe tail box and of sumcient vertical dimension to provide for the freepassage of the stream of gases, which is divided into two divergingbranches by the baflle. A horizontal rib Ha at the front of the baffle His preferably provided to facilitate the division of the gas into twodiverging streams.

The baflie is arcuate in its vertical crosssectional characteristic,having its concave surface faced toward the baflle l1.

The baflle 20 extends to the full width of the tail box I! and issecured at its ends thereto as by flanges 2|. The baflle 2D is steppedback from the baille l1 sufficiently to form between the two baflies thearcuate passage 22 of sufficient capaciltsy to receive the gases passingfrom the passages The baflle 20 spans the full height of the tail box Iand is provided at its center with a horizontally elongated port 23extending from side to side of the tail box, and through which thetraveling gases pass rearwardly. The port 23 is of sufficient capacityto prevent restriction of the travel of the gases.

Next in the rear of the bafile 20 is the horizontal arcuate baflie 24having its concavity toward the baflle 20 and spaced therefrom toprovide the passage 25. Like the baflles I1 and 20, the baille 24extends from side to side of the tail box I and is secured in positionas by the end flanges 25a. The vertical extent of the bafiie 24 is suchas to form between its horizontal edges and the top and bottom walls ofthe tail box the ports 26 for the escape rearwardly of the gases passingthrough the port 23 and passage 25. The top and bottom walls of the tailbox preferably diverge somewhat adjacent its rear end, as indicated at21 in Fig. 2, to provide ample capacity for the ports 26 to permit thefree flow of the gases without restriction.

The ports 26 may be provided with screenin as shown at 21, to furtherreduce sound.

Again the rear baflle 24a may span the full height of the tail box, asillustrated in Fig. 8, and be provided with a plurality of perforationsand ports, such as indicated at 24b, spaced over its area for the escapeof the gases.

Insulation may be applied exteriorly' of the body 10 as indicated at 28,and also may be applied to the walls of the tail box as indicated at 29.

In Fig. 4 I indicate a convenient manner in which the mufller may beinstalled in the nacelle or covering 36 of a motor which is installed onthe-wing 3| of an airplane. In this instance the rear end of the nacelleis sheared oil and the tail box mounted flush therewith. Thus the tailbox is adjacent the upper surface of the wing where the drag or suctioneffect is very great.

In Figs. 5 and 6 I show the application of the principles of myinvention to a motor mounted in the fuselage 82 of an airplane, themuffler being mounted in. the airfoil 33 built close to the wing 34. Theexhaust of the motor is led to the body ID by means of the connectingpipe 35.

In Fig. '1 I show the miller applied to the back or rear end of anautomombile where the suction effect is great and commensurate withspeed, the pipe 36 leading from the exhaust manifold of the engine tothe body I!) and the tail box I assembly which is mounted under theferred embodiment of my invention but it should be obvious or understoodthat a very important part of my invention, namely, the tail boxarrangement for suction effect upon the exhaust,

can be applied with some degree oi advantage to other or common types ofmuillers.

I claim:

1. An improved baflle structure for the exhaust gases of internalcombustion engines, comprising walls deming a compartment having a longslotted opening in its front wall for the admission of the gases in theform of a wide shallow stream, baille means within the compartment todivide such stream into two diverging shallow sub-divisions flowingrearwardly, a second baiiie means in the rear of the first baiiie meansto direct said sub-divisions toward each other, and an outlet for theescape of gases from the second balile means.

2. An improved baille structure for the exhaust gases of internalcombustion engines, comprising walls defining a compartment having alongslotted opening in its irontwall for the admission of the gases inthe form of a wide shallow stream, baille means within the compartmentto divide such stream into two diverging shallow sub-divisions flowingrearwardly, a second baflie means in the rear of the first baille meansto direct said sub-divisions toward each other, and a long slottedopening in the second baflle means for the escape of the gases past thelatter.

3. An improved baille structure for the exhaust gases of internalcombustion engines, comprising walls defining a compartment having along slotted opening in its front wall for the admission of the gases inthe form of a wide shallow stream. bafiie means within the compartmentto divide such stream into two diverging shallow sub-divisions flowingrearwardly, a second bafile means in the rear of the first baiile meansto direct said sub-divisions toward each other, a long slotted openingin the second baflle means for the escape of the gases past the latter,and a third baiile means to again divide the gases into two wide shallowstreams as they emerge from the compartment.

4. An improved muiller structure for the waste gases of an internalcombustion chamber comprising walls defining a pair of chambers, one ofsaid chambers having an inlet opening at one end to be connected to theexhaust of the engine and a widely extended outlet opening at theopposite end for the escape of the gases and. the walls of the chamberrelatively disposed to form the gases traveling from the inlet openingto the outlet opening in a thin widely extended stream, the secondchamber having an inlet opening connected to the outlet opening of thefirst chamber and an outlet opening at the opposite end, and baillemeans in the second chamber interposed in the path of the stream ofentering gases and dividing the same into two diverging thin streamswhich pass rearwardly toward the outlet opening of the second chamber.

5. An improved mufller structure for the waste gases of an internalcombustion chamber comprising walls defining a pair of chambers, one ofsaid chambers having an inlet opening at one end to be connected to theexhaust of the engine and a widely extended outlet opening at theopposite end for the escape of the gases and the walls or the chamberrelatively disposed to form the gases traveling from the inlet openin tothe outlet opening in a thin widely extended stream, the second chamberhaving an inlet opening connected to the outlet opening of the firstchamber and an outlet opening at the opposite end, baflle means in thesecond chamber interposed in the path 01 the stream of entering gasesand dividing the same into two diverging thin streams, and second bumemeans at the rear of the first baiile means intercepting said twostreams and uniting them into one widely extending and thin stream asthey pass toward the outlet of the second chamber.

6. An improved muiiler structure for the waste gases of an internalcombustion chamber comprising walls defining a pair of chambers, one ofsaid chambers having an inlet opening at one end to be connected to theexhaust of the engine and a widely extended outlet opening at theopposite end for the escape of the gases and the walls of the chamberrelatively disposed to form the gases traveling from the inlet openingto the outlet opening in a thin widely extended stream, the secondchamber having an inlet opening connected to the outlet opening of thefirst chamber and an outlet opening at the opposite end, baffle means inthe second chamber interposed in the path of the stream of enteringgases and dividing the same into two diverging thin streams which passrearwardly toward the outlet opening of the second chamber, and meansfor again dividing the stream of gases as they escape from the secondchamber.

7. An improved mufiier structure, for the waste gases of an internalcombustion engine employed to drive an airplane or other vehicle,comprising walls defining a pair of chambers, one of said chambersserving to absorb the firing noises and having an inlet opening at oneend to be connected to the exhaust of the engine and a widely extendedslot-like outlet opening at the other end for the escape of the gases,and the walls of the chamber being relatively disposed to spread thegases traveling from the inlet opening to the outlet opening in a thinwidely extended stream, the second chamber having an inlet openingcorresponding in dimensions to the outlet opening of the first chamberand communicating therewith for the unobstructed emission of the streamof gases from the first chamber into the second chamber, and the secondchamber having an out let opening into atmosphere in the area of lowpressure resulting from the travel of the airplane to facilitate thesuction withdrawal of the stream of gases from the first chamber.

8. The structure of claim 'I, wherein the crosssectional area of thesecond chamber adjacent its inlet opening is greater than thecross-sectional area of the first chamber adjacent its outlet opening.

9. An improved mumer structure for silencing the stream of exhaust gasesof an internal combustion engine, comprising walls defining a chamberhaving a centrally disposed inlet in its front arranged to be connectedto the exhaust of the engine, the side walls of the chamber divergingfrom said inlet opening and the top and bottom walls of the chamberconverging from the front of the chamber toward the rear end of thechamber, and an extended slot-like outlet opening at the rear end of thechamber extending from one side wall to the other to spread the gases asthey pass through the chamber into a thin widely extending stream.

10. The structure of claim 9 wherein the interior of the chamberadjacent its inlet opening is provided with a laterally extending baiileto facilitate the spreading of the gases toward the side walls of thechamber.

JOHN A. FISHER.

